1. Field of the Invention
The present invention relates to a tympanic membrane prosthesis and in particular to the mechanical fixation of a synthetic prosthesis to the tympanic membrane to act as a substrate or stimulant for cell growth and healing.
2. Description of the Related Art
The tympanic membrane or as it is often referred to, the eardrum, is the layer of tissue that separates the outer ear canal from the middle ear. The middle ear contains the bones responsible for conducting or transmitting sounds to the inner ear and then on to the brain. The tympanic membrane is responsible for receiving sound pressure waves and transmitting them to the bony apparatus inside the middle ear. The tympanic membrane is typically located more than 20 mm inside the ear canal but can be visualized by spreading the soft outer portion of the canal with a speculum and looking through either a hand held otoscope or through a larger oto-microscope.
The tympanic membrane can be perforated as a result of a variety of different processes such as infections of the middle ear, direct trauma or poor post-operative healing. While perforations of the tympanic membrane do not present an immediate danger to the patients hearing apparatus, they can lead to decreased hearing, autophony (hearing an echo of ones own speech), or pain secondary to infection. Tympanic membrane perforations can be subcategorized based on the duration of the perforation, i.e., acute verses chronic, and the presence or absence of drainage i.e., dry verses wet. These subcategories have an effect on a prognosis of a given perforation. For example, acute dry perforations such as those resulting from a direct trauma to the eardrum from a sharp instrument often or usually heal spontaneously. On the other hand, patients with acute or chronic otitis media can develop chronic perforations having a duration of longer than two months that can remain unhealed for periods longer than a decade. The relatively common use of pressure equalization tubes in children with recurrent otitis media has also resulted in an increase in chronic perforations in these young patients.
In response to this pervasive problem, many techniques have been developed for the closure of tympanic membrane perforations. Myringoplasty is a procedure wherein the eardrum is patched with a graft material, such as muscle fascia. It has a success rate that often exceeds 95% but involves the use of an operating room, anesthesia and an incision to harvest the graft material. These factors not only expose the patient to risks of infection, bleeding, anesthesia, hearing loss, etc., but also result in high medical costs. Non-surgical techniques, on the other hand, can provide the benefit of decreased risk and discomfort for the patient as well as decreased cost. Thus, many non-surgical approaches to the healing of tympanic membrane perforations have been developed including rice-paper patches and growth stimulants applied to the perforation periphery. Such techniques, however, have met with only limited success and studies of their efficacy have been conducted mostly in animal models or in small numbers of human patients in uncontrolled studies in Europe. Thus, their efficacy remains unclear.